class jQuery {
    constructor(selector) {
        const result = document.querySelectorAll(selector)  // DOM查询
        const length = result.length
        for (let i = 0; i < length; i++) {
            this[i] = result[i]
        }
        this.length = length
        this.selector = selector
    }
    get (index) {
        return this[index]
    }
    each (fn) {
        for (let i = 0; i < this.length; i++) {
            const elem = this[i]
            fn(elem)
        }
    }
    on (type, fn) {
        return this.each(elem => {
            elem.addEventListener(type, fn, false)
        })
    }
    // 还可以拓展很多API
}

    //插件
    jQuery.prototype.dialog=function(info) {
    alert(info)
}

//基于 jQuery "造轮子"
class myjQuery extends jQuery {
    constructor(selector) {
        super(selector)
    }
    // 扩展自己的方法
    addClass () {

    }
}

// 测试
const $p = new jQuery('p')
$p
// jQuery {0: p, 1: p, 2: p, length: 3, selector: "p"}

$p.get(1)
{/* <p>文字2</p> */ }

$p.each((elem) => console.log(elem.nodeName))
// ppp
$p.on('click', () => alert('clicked!'))

$p.dialog('abc')
// abc